How to catch rejected graphql subscription in jest / apollo client?

Question

Using graphql-yoga I am attempting to write jest tests to cover subscriptions.

I am able to successfully test the happy path were a subscription works (with auth). Unfortunately I am not able to test the situation where a subscription websocket connection is rejected.

In my server setup I reject any websocket connections that do not pass my auth criteria:

const app = await server.start({
    cors,
    port: process.env.NODE_ENV === "test" ? 0 : 4000,
    subscriptions: {
      path: "/",
      onConnect: async (connectionParams: any) => {
        const token = connectionParams.token;
        if (!token) {
          throw new AssertionError({ message: "NO TOKEN PRESENT" });
        }
        const decoded = parseToken(token, process.env.JWT_SECRET as string);
        const user = await validateTokenVersion(decoded, redis);
        if (user === {}) {
          throw new AssertionError({ message: "NO VALID USER" });
        }
        return { user };
      }
    }
  });

(https://github.com/jakelowen/typescript-graphql-boilerplate-server/blob/master/src/startServer.ts#L87)

Now in my relevant tests: https://github.com/jakelowen/typescript-graphql-boilerplate-server/blob/master/src/modules/counter/counter.test.ts

The first test (the happy path) passes as I would hope:

// works as expected.
  test("should start a subscription on network interface and unsubscribe", async done => {
    const client = new TestClientApollo(process.env.TEST_HOST as string);
    await client.register(email, password);
    await User.update({ email }, { confirmed: true });
    await client.login(email, password);

    // set up subscription listener
    const sub = client.client.subscribe(defaultOptions).subscribe({
      next(result) {
        expect(result).toEqual({
          data: {
            counter: {
              count: 0
            }
          }
        });
        sub.unsubscribe();
        done();
      }
    });
  });

Then I try 3 different ways to catch the expection I expect to see in unauthed scenarios. None of these tests pass as I would hope:

// Does not work! I am expecting an error.
  test("Unauthed subscriptions are rejected", done => {
    const client = new TestClientApollo(process.env.TEST_HOST as string);

    const sub = client.client.subscribe(defaultOptions).subscribe({
      next(result) {
        expect(result).toEqual({
          data: {
            counter: {
              count: 0
            }
          }
        });
        sub.unsubscribe();
        done();
      }
    });

    // Received value must be a function, but instead "object" was found
    expect(sub).toThrow();
  });

  // does not work
  // Error: Uncaught { message: 'NO TOKEN PRESENT' }
  test("Unauthed subscriptions are rejected second attempt", done => {
    const client = new TestClientApollo(process.env.TEST_HOST as string);

    try {
      const sub = client.client.subscribe(defaultOptions).subscribe({
        next(result) {
          expect(result).toEqual({
            data: {
              counter: {
                count: 0
              }
            }
          });
          sub.unsubscribe();
          // done();
        }
      });
    } catch (error) {
      console.log(error);
      expect(error).toEqual({
        message: "NO TOKEN PRESENT"
      });
      done();
    }
  });

  // does not work
  // Error: Uncaught { message: 'NO TOKEN PRESENT' }
  test("Unauthed subscriptions are rejected second attempt", done => {
    const client = new TestClientApollo(process.env.TEST_HOST as string);

    try {
      const sub = client.client.subscribe(defaultOptions).subscribe({
        next(result) {
          expect(result).toEqual({
            data: {
              counter: {
                count: 0
              }
            }
          });
          sub.unsubscribe();
          // done();
        }
      });
    } catch (error) {
      console.log(error);
      expect(error).toEqual({
        message: "NO TOKEN PRESENT"
      });
      done();
    }
  });

  // does not work
  // Expected the function to throw an error.
  // But it didn't throw anything.
  test("Unauthed subscriptions are rejected third attempt", done => {
    const client = new TestClientApollo(process.env.TEST_HOST as string);

    expect(async () => {
      const sub = await client.client.subscribe(defaultOptions).subscribe({
        next(result) {
          expect(result).toEqual({
            data: {
              counter: {
                count: 0
              }
            }
          });
          sub.unsubscribe();
          done();
        }
      });
    }).toThrowError();
  });

  // does not work
  // Expected the function to throw an error.
  // But it didn't throw anything.
  test("Unauthed subscriptions are rejected fourth attempt", done => {
    const client = new TestClientApollo(process.env.TEST_HOST as string);

    const attempt = async () => {
      const sub = await client.client.subscribe(defaultOptions).subscribe({
        next(result) {
          expect(result).toEqual({
            data: {
              counter: {
                count: 0
              }
            }
          });
          sub.unsubscribe();
          done();
        }
      });
    };

    expect(attempt).toThrowError();
  });

Any idea how to expect the assertion error I am expecting in a test for the unauthed scenario?

full repo here: https://github.com/jakelowen/typescript-graphql-boilerplate-server

Answer 1

Booyah. I read up on observables in general and observable.subscribe() in particular and discovered that the second optional parameter is an onError callback function. Refactoring the test to:

test("Unauthed subscriptions are rejected", done => {
    const client = new TestClientApollo(process.env.TEST_HOST as string);
    // jest.setTimeout(1000); // increase timeout
    client.client.subscribe(defaultOptions).subscribe(
      res => {
        console.log(res);
      },
      err => {
        expect(err).toEqual({ message: "NO TOKEN PRESENT" });
        done();
      }
    );
  });

And all works as expected. Hooray!

Side editorial: It is a bit amazing to me that after dozens of hours of google, stack overflow, and github searches that I never found a simple, clear cut tutorial on how to properly test graphql subscriptions.